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Author Topic:   metric ring end gap
awkwardjeff
Member
posted July 18, 2004 05:14 AM
I built a motor this year with JE pistons and metric rings. Motor temp was NEVER over 220 and that was a night with a heavy track and a radiator full of mud. Every other night the motor runs 200. I forget what I set the end gap at........but the motor leaked 2% when it was fresh......then we didn't leak it again until yesterday, it now leaks 18%......... total of 18 nights

My questions are what should the end gap be for the top and 2nd rings be? And is this about average for these rings to fall off this soon? Also the combustion chambers were full of carbon and the heads were new with seals so I feel it pulled oil past the rings..........

This motor made lots of power when fresh, just seemed to drop off much faster then my total seal rings I normally use, I guess it's just that old deal ......you want power or you want long life........ I don't mind re-ringing a motor but not ever 8-12 nights.

any thoughts???

[This message has been edited by awkwardjeff (edited July 18, 2004).]

sdhnc29
Member
posted July 18, 2004 12:34 PM
Jeff,

Which ring pack did you use? What is the bore size, and what stone was used to finish the bore?? Also, were the pistons gas ported?

Steve

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780
Check out my other business at www.solemnvow.com A special thanks to jammin for the awesome job he has done for me on this site!!


awkwardjeff
Member
posted July 18, 2004 01:04 PM
Steve I was hoping you would reply, You seem to have great knowledge in these matters.

The bore size is a 4.030, yes the pistons have gas ports to the top ring..... bore finish i'm unsure of..... this machine shop I use has done my work for years and everything is always perfect. Builds many sprint and Late motors with metric rings so I assumed he knew the bore finish would be different then my standard deal. The bores look MUCH smoother then my standerd deal though.... not a scuff in any pistons or bores, everything looks like new inside, will re-use bearings...... H bearings and only 11.5 to 1 compression.

As far as ring pack??? 1.5 top 1.5 2nd groove and a 3 oil ring...... I don't recall the brand name off the top of my head.

I do remember not having instructions in the box to set end gap....... and being my first time with the metric rings I called the machine shop and went with what they said..... seems to be if I remember correctly.....I set the top at .018, 2nd groove at .014.......... that's a few thousands tighter then I normally use on a 1/16 with a gapless 2nd groove. I would THINK that with less surface area of the ring contacting the bore would be less heat and less expansion to close the gap.... I was thinking the metric rings should have been tighter, but didn't want to ruin a pile of parts learing what this new motor needed. So I set them a little loose and with freshen up sooner....... would like to get 20-25 shows between re-ring.

I dropped the heads off this morning for a set of springs and a bath, They were perfect minus the carbon in the chambers. Plugs also looked perfect, no carbon on plugs some very small oil deposits, This is NOT a over rich condition.....this is a ring seal problem.



sdhnc29
Member
posted July 18, 2004 10:29 PM
Hey Jeff,

You actually have the ring gap a little too tight. Set the top ring at .020" and the second ring at .022". This ring gap setting will not allow the top ring to get unloaded, and is worth a bit of power. We've seen 15hp gain's in just changing the ring end gap. I think you were trapping gas between the top and second ring, which will add to the ring seal problem. I'd also make sure that a torque plate was used on the final hone. This is extremely important with the gas ported light tension ring's! Have a good look at the top of the bores. If you see shiny places in the cylinder next to each head bolt hole, usually extending down the bore about 1"-2", then you will know that the block did not have a torque plate on it when the bores were finished. Or, you will know that something is different from when the block was finished to when it was assembled. Such as the torque plate was put on with bolt's, and you assembled the engine with stud's, or vise-versa. This is quite common to see, and it makes a HUGE difference in the bore distortion, and ultimately ring seal.

The bore finish is also important. You might ask what stone they used to finish the bore's.

We actually have not used 1.5mm ring's in about 5 or 6 year's. We have been using the .043"-.043"-3mm ring pack in everything that we build, with lateral gas ported piston's. Our late model engines get freshened at no more than 500 miles, and we have not seen any excessive ring wear, unless of course the engine had been inhaling dirt. I've got a few lower division engines that must have at least 20-25 night's on them, and no complaint's from the customer's about blow-bye. If this engine that you did was for a dirt car, 20-25 show's is pushing it if it's in a real dusty environment.

Steve

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780
Check out my other business at www.solemnvow.com A special thanks to jammin for the awesome job he has done for me on this site!!


awkwardjeff
Member
posted July 18, 2004 11:01 PM
Steve,
Thanks for your reply, your thoughts are greatly appriecated. I just want to DOUBLE check with you ......

.020 on TOP ring?
.022 on 2nd ring?

to me that sounds like you mixed them up...top ring should have more clearance because that is were the heat is and heat is what cause the rings to expand and close the gap to seal........ so if this is correct can you explain this???

You were right about some combustion (trapping gas) between the top and 2nd rings....... on about half the pistons.....and seems like only a night or two......because these pistons had VERY-VERY LITTLE traces of carbon between rings......

Also, Blocks are ALWAYS bored and finished with plates, and if using studs I have the studs in before the plate goes down.....if bolts are used I let the machine shop just use bolts....... he HATES when I install the studs just for him, something about them being in the way....LOL But I like you don't want distortion in the bore on top were the ring needs to seal the best.

Also, This person I built the motor for didn't complain about power. It's something the builder picks up on though..... I know this time of year everyones motor is getting tired unless it's already exploded and they needed to put in a new motor.....LOL He had a distributor problem on Friday night AFTER a rock broke the fuel pump off the block. I had him pull the rockers off and headers off so I could leak it...... Like I said I wanted to see where this motor was at now. And since he leaned it out, pounded the pistons with timing I thought this was the perfect time to check....... Then I had him pull out and I took it apart and cleaned every thing for re-assembly... Just waiting for heads and rings. They took the motor out of the spare car and installed that in the main car...... I guess the spare motor on the floor isn't good enough....LOL too much energy and too much money these kids got today....

Steve, Thanks again. just a double check on top and 2nd.......

sdhnc29
Member
posted July 18, 2004 11:18 PM
Yes Jeff, .022" on the second ring is correct. This keep's combustion gas from getting trapped and unloading the top ring. We've been doing this for quite some time now, and it works well. Your driver will like the extra power too, and it's noticeable ;-) The second ring is only a s****er, so the extra gap does nothing to change this affect. Most ring manufacturer's are now recommending this as well, other than applications with big NOS load's where they use the "hel-fire" ring's.

Steve

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780
Check out my other business at www.solemnvow.com A special thanks to jammin for the awesome job he has done for me on this site!!


awkwardjeff
Member
posted July 18, 2004 11:33 PM
Steve,

Thanks again for the reply, and sooo fast, After re-reading the 2nd reply I understood what you were getting at with the wider gap on 2nd groove......... and that makes sense now.

This is a PERFECT example of why this forum is the BEST...... got a question, get a straight answer with a good explaination from someone with knowledge.......

Thanks for all the information, and help learning more information, not just myself but many other people learn by reading, that is why no question is stupid........

Jeff

[This message has been edited by awkwardjeff (edited July 18, 2004).]

Raz_900
Member
posted July 19, 2004 02:00 PM
Great advice from Steve again!!!

The only other thing I'll add is to make sure the motor gets broken in right. I see about a half dozen motors blow at my track every spring. First night out, beat the daylights out of it and it yaks. And of course it's the motor's/builder's fault.

On the first night, I try to keep mine under 2/3 throttle and 5000 rpms during warmups. Then under 6000 and 3/4 throttle in the heat race. For the feature, run it at about 85%. Change oil again during the week then have at it.

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